minions hurt, especially early level. Almost never go for a fight if the enemy got creep advantage or you lose the fight due to creep damage

whenever you attack someone with basic attacks, minions will start attacking you. Keep that in mind when trading. However, most spells won't trigger minion aggro so you can harass with spells without having to worry about creep damage

bushes remove minion aggro (unless it is warded - that's also a way of checking if a bush is warded or not)

don't be overly aggressive if you don't know where the enemy jungler is and you can't handle 1vs2

always try to push the lane before you go shop so you miss less xp

that said, dont waste your time by going back too often. I often see people basing for no real reason. Try to only base when you can shop something or you need to heal

most of the time you want to shop at the same time when the enemy laner goes shopping or you are at an item disadvantage

move to your lane as fast as possible after shopping. You can already start running and buying the moment you spawn in your base to get back a few seconds faster to lose less time

beware the enemy items. If you are vs. a Riven top with a red pot, be careful and don't fight him her early

watch levels: If you are still lvl 1 and the enemy hits lvl 2 before you, this can be a big problem in certain matchups. This is also true if the enemy laner hits 6 before you and he might all-in you

if you are losing a lane, try to stay at least in range of xp and don't go for 1vs1 anymore unless you have your jungler (and they dont have theirs)

know the strenghts/weaknesses of each champ and especially the one you are playing. If you play Lee Sin, you are strong early game so use this to your advantage. If you play something like Tristana, you don't need to make plays early and just play it safe and farm up

when your team is behind, don't force fights out of despair. Instead, try to stall and wait for them to make mistakes

it's okay to give dragons/towers or even kills up. Don't try to defend or fight for something if you are not in a position to do so. Better give 1 dragon up than losing an extra 3 people and possible more towers for trying to defend it

communicate with your team and use pings

call your jungler if you know you can dive him or can get a kill on him. Also tell your jungler if key abilities like ults or flashes are down for the enemy laner and where his wards are

be smart when buying items. Rushing t2 boots is rarely a good idea (unless jungler and +5 boots) and just a gold sink that can be better used on other stats

when you need to facecheck something, always try to let the most tankiest member go in front and facecheck it

you don't always need to win your lane. It's okay to lose the lane if you are only 1 kill and 30cs behind. Play defensive and accept it and don't try to force a comeback only to be 5+ kills and 70+cs behind in the end

runes and masteries. Do some research (guides) or watch some profiles from other players and get a basic idea what runes and masteries you should run on what champion. These are important to get an advantage early in lane or manage bad matchups

try to get used to level up your skills by using crtl + hotkey for the spell. It's faster and it can make the difference between winning a fight or not if you can quickly level up the skill in a fight.

Jungle

do your buffs early and don't delay them or the enemy will take advantage of this and steal them

respawn timers for buffs/drake/baron: 5/6/7 minutes

when you need to smite secure an objective, combo your smite with an ability. This means that you use a skill + smite at the same time so you have more burst to not get it stolen away

if you gank a lane successfully, 95% of the time it's best to help the laner push the lane so he can base and the enemy loses xp

if you need to hold a lane because your laner died, you can either push or freeze the lane. Try always to freeze it unless your lane is pushing anyway. In this case push it as hard as you can into the tower so it resets and the enemy can't freeze it

try to gank the lane that has the most cc on your team. This will give you a higher chance of getting kills and snowball the lane

dont waste time ganking lanes that have no real cc vs. good escape spells on enemy team. For example if you have a Nidalee mid vs. Zed and you play Nocturne jungle, unless Zed overextends a lot this gank is not gonna work and you waste a lot of time

only help losing lanes up to a certain point. You can maybe recover a lane that is 2 kills behind, but any more than that is usually not worth the time/effort you put into the lane to bring it back. Worst case is that you lose 1vs2 and the game gets out of control. Just ignore the lane and focus on the remaining 2

dont feed double buffs. This is crucial early game and can cost the lane if not the entire game. When in doubt, play defensive and don't risk feeding double buffs

do not counterjungle when your team is behind. It's way too risky if you don't see the enemy team

learn to predict the enemy jungler and countergank. This is done by watching your lanes and see who's overextended the most and just wait in the brush. Chances are, the enemy jungle will gank the lane any time soon

if you play jungler with a very strong lvl 6 (Amumu, Vi, Nocturne) try to use it on cooldown and gank with them to get kills/objectives

junglers are often still a second support. So buy wards and help your team get wards up

when donating a buff, press s to stop attack

when there is no laner in a certain lane and the minions are dying to tower, go there and take the xp/farm from it. They are more worth than jungle camps

don't force ganks. If there is no lane to gank for you and no opportunity to countergank, just farm up

don't gank a lane the moment your laner got 20 creeps at his tower. It's not worth the maybe kill if he loses all that gold and xp from the creeps

presence enough by buying pink wards for top/bot or showing yourself without doing anything helps your lane out by making the enemy lane play more carefully

Top

know matchups. It's really important for toplane and it only comes with experience

that said, don't pick champions because x counters z. If you can't play x, don't pick him and play a champion instead that you are familiar with

most of the time the first gank happens top lane. If you know you can't win 2vs2 with your jungler, don't push early and play it safe

a lot of people make the mistake of not pushing the lane top completely to the tower. Use this to your advantage and try to freeze the lane near your tower so can deny him farm and be safe from ganks

when freezing a lane, don't let it push too hard. Kill just enough creeps so that it barely pushes into your direction or you might die in a dive/gank due to too much creep damage

when you need to base and you can't push it but it pushes into your direction, just base and it will still push into your direction when you come back. This is better than getting denied by the enemy freezing the lane

when losing a lane, go tanky. If you build damage and the enemy is smart, he will keep killing you because he will have more damage than you. You won't be useful this way later on as opposed to being a tank that can still help your team

dont call or blame the jungler if you are unsure about getting a kill. A fail attempt will just put you even more behind

if they are 5man grouped to take dragon and you have no TP and can't join them, push the tower and try to trade tower for drake

Mid

don't forget to auto attack for harass. People in lower ELOs seem to just use a spell instead of spell+auto, which is a lot more damage

push for a faster lvl 6 than enemy laner if you play a strong lvl 6 champ like Annie, Ahri, Zed, Fizz to maybe abuse it and get a free kill on them

only roam if you can guarantee a kill. Don't waste your time going bot if you have no CC and can't make anything happen or you will lose too much farm

when you can't follow the enemy laner who left the lane to roam, push the lane and try to get his tower in return

if you have the champion to do so, farm the jungle (wraith/wolves) to get an advantage over the enemy laner

AD Carry

watch the health of your own minions and try to auto the enemy ad carry when he goes for a last hit. Either he will lose the trade because he goes for the last hit or he will lose the last hit

if the enemy bot lane is pushing hard for a lvl 2, try to counterpush and not get pushed in

if you can get lvl 2 before them, you can use this to your advantage and force a fight

it's smart to sacrifice some cs if you can harass them instead and win the lane because of this. But it's not a good idea to give cs up for free if you can't get an advantage out of it

watch the enemy items and try to trade with them if you know you can win. If you have a Doran + BF vs. 2 Doran + Lifesteal + Boots, you have a lot more damage and should win a fight. Be smart about something like this and use this to your advantage

if you have sustain by having lifesteal or with your support and the enemy doesn't have sustain, go for a lot of trades to slowly but surely get them low and force them out of lane

focussing the support is often a better choice if you can burst him down and the enemy ad carry has a strong escape that makes killing him hard. If you are a Graves+Blitz lane vs. Sona+Ezreal, grabbing Sona and going for her is the better choice

keep your farm up! dont stop farming just because you killed the tower and mid-game started

when teamfighting it's often better to play safe and hit what you can hit without putting yourself in danger than going for high priority targets and die

that doesn't mean you should focus the tanks all the time if there are other targets availabe to you that you can safely hit

practice orb walking and move between attacks to position yourself while still doing damage in fights

hit the towers when you are sieging late game and you can hit it. But don't risk getting caught so better safe than sorry

it's good to get defensive items when you are ahead and you can rely on your team to do damage

if your team doesn't have a lot of damage and your team is behind, you can't afford to get defensive items or you won't be able to win teamfights due to a lack of damage. You need to risk relying on your position and pray to survive

Support

you can often win or lose the bottom lane by your playstyle alone

your auto attacks hurt a lot early levels, so use them on the enemy ad carry (or support) when they go for a last hit and are out of position

your main job in laning phase is to show presence. This is done by actively harassing them

remember to keep your wards up and tell the ad carry to back off or be careful when you leave the lane to ward or need to shop to get new wards

pink wards apply a lot of pressure. Use them and tell your jungler to gank especially when you are behind in lane: go get the pinks

when you need to base, help your ad carry to push the lane if he wants to leave the lane too but dont screw up his cs and attack minions that he is attacking

your #1 priority should be vision and map control in mid and end game

this means that rushing a sight stone is often your best choice

getting gp10 is okay but still remember to get your wards to be safe in lane till you get your sight stone

I see a lot of supports (especially Zyra) getting damage items. Thats fine but don't neglect vision for it

an early oracles in mid game can snowball the game a lot in your favour

if you have oracles, tell your team to group with you so you can clear the wards safely

just because you have sight stone doesn't mean you should stop buying regular wards. Keep buying and placing them

when you are behind in a game, a good tactic is to regain control of your jungle and hope for picks so you can get back into the game. This is done by buying oracles and a lot of wards and hope for a picks

if your jungler doesn't do it, keep timers for at least drakes and baron and tell your team when they're up

try to keep up in xp. Don't leave a lane when there are many creeps and soak up the xp

don't use your skills in teamfights instantly but instead save them for when you need them to peel for your ad carry. Using a random Janna Q won't help your team as much as having it available for when a Riven tries to assassinate your ad carry

Basic tips for each role (Reddit)http://www.reddit.com/r/leagueoflegends/comments/1oui1z/basic_tips_for_each_role_from_a_diamond_player/